1. Field of the Invention
This invention relates to a still image recording apparatus of the kind recording a still image on a magnetic disc or the like.
2. Description of the Related Art
An SV (still video) system has been known as a system of, for example, recording a still image of the NTSC color system on a two-inch magnetic disc. A system called CHSV (format compatible high definition SV) system which permits recording of an image with such high picture quality as having 1000 picture elements (in the vertical direction).times.1300 picture elements (in the horizontal direction) on an SV floppy disc (the magnetic disc) and is arranged to have interchangeability with the conventional SV system has recently been proposed. The CHSV system is briefly described in outline below as the details of this system are well known.
The CHSV system uses a method for analog transmission of sample values. This method is used also for the MUSE (multiple sub-Nyquist sampling encoding) system which is known by the name of an HDTV (high definition television) transmission system. According to this analog transmission method, an analog transmission path on which a given band limit is imposed is used for correct transmission of a train of sample values (at intervals of time T). The analog transmission of sample values requires the following two conditions (a) and (b):
(a) The frequency characteristic of the analog transmission path has a linear phase and is of a symmetric roll-off characteristic centered at the frequency of 1/2T (Nyquist condition). PA1 (b) A correct sampling point can be re-sampled on the signal receiving side for reproduction. PA1 Notes: In these tables, n represents 0, 1, 2, 3, - - - .
The CHSV system is basically arranged to record and reproduce, on these two conditions, a train of sample values of a video signal on and from an SV floppy disc in conformity with the recording format of the conventional SV system.
FIG. 1 schematically shows the above-stated analog transmission of sample values. Referring to FIG. 1, a signal transmission path 201 has an LPF (low-pass filter) characteristic. Sampling means 202 is arranged to perform re-sampling. An input signal to the transmission path 201 is band-limited by means of an LPF 2001. The band-limited signal is frequency-modulated by a frequency modulation circuit 2002. The frequency-modulated signal is magnetically recorded on an SV floppy disc 2003 through an electromagnetic conversion system. A signal which is reproduced from the SV floppy disc 2003 is demodulated by a frequency demodulation circuit 2004. The demodulated signal is outputted and supplied to the above-stated sampling means 202 through an LPF 2005.
Further, FIGS. 2(a), 2(b) and 2(c) show the sample patterns of a luminance signal Y and color-difference signals C1 and C2 to be recorded on the SV floppy disc by the above-stated CHSV system. In this instance, color-difference signals R-Y and B-Y are shown as the color-difference signals C1 and C2 for sorting the sampling points. Therefore, if the signal C1 represents the color-difference signal R-Y, the signal C2 represents the color-difference signal B-Y. If the signal C1 represents the color-difference signal B-Y, the signal C2 represents the color-difference signal R-Y. In the CHSV system, each of the signals Y, C1 and C2 having the sample patterns shown in FIGS. 2(a), 2(b) and 2(c) is divided into four kinds, and the four kinds of signals are recorded in four tracks on the SV floppy disc. For this purpose, the signals Y, C1 and C2 are respectively divided in different manners as shown in Tables 1, 2 and 3 below: